WO2022086598A1

WO2022086598A1 - Image scanning apparatus for compensating optical flare

Info

Publication number: WO2022086598A1
Application number: PCT/US2021/035356
Authority: WO
Inventors: Kyoungrok KIM
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2020-10-19
Filing date: 2021-06-02
Publication date: 2022-04-28
Also published as: KR20220051655A

Abstract

An example image scanning apparatus includes a sensing device to scan a document, a memory, and a processor to, based on a scan command regarding a document having a changeable ratio between a black area and a white area in a sub-scan direction being input, calculate a flare factor for flare compensation by using a plurality of signal values output from the sensing device regarding the document, store the flare factor in the memory, based on the scan command being input after calculating the flare factor, compensate a signal value output from the sensing device by using the stored flare factor, and generate an image by using the compensated signal value.

Description

IMAGE SCANNING APPARATUS FOR COMPENSATING OPTICAL FLARE

BACKGROUND

[0001] An image scanning apparatus may refer to an apparatus which scans an original image of a document, a drawing, a film, etc. to convert the image into digital data. In this case, the digital data may be displayed on a monitor or printed by a printer to be generated as an output image. Examples of such an image scanning apparatus include a printer, a scanner, a copier, a facsimile, or a multi-function peripheral (MFP) including functions of these in combination as one apparatus, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 is a block diagram illustrating an image scanning apparatus according to an example;

[0003] FIG. 2 is a block diagram illustrating an image scanning apparatus according to an example;

[0004] FIG. 3 is a diagram illustrating a shape of an image scanning apparatus according to an example;

[0005] FIG. 4 is a diagram illustrating an example of an image included in a test document;

[0006] FIG. 5 is a diagram illustrating an operation of calculating a flare factor according to an example;

[0007] FIG. 6 is a diagram illustrating an image scanning apparatus including a plurality of image sensors according to an example;

[0008] FIG. 7 is a diagram illustrating an operation of calculating a flare factor for each of a plurality of image sensors according to an example; and

[0009] FIG. 8 is a flowchart illustrating a method for controlling an image scanning apparatus according to an example. DETAILED DESCRIPTION

[0010] Hereinafter, various examples will be described with reference to the drawings. The examples described hereinafter may be modified and practiced in various different aspects.

[0011] In the disclosure, the expression that a certain component is “connected” to another component not only includes a case where the components are “directly connected to each other,” but also a case where the components are “connected to each other with another component interposed therebetween.” In addition, when a certain component “includes” another certain component, it includes a case in which still another component may be further included, rather than excluding it, unless otherwise noted.

[0012] In the disclosure, an “image forming job” may refer to various jobs relating to an image such as forming of an image or generating, saving, or transmitting of an image file (e.g., printing, scanning, copying, or faxing), and the “job” may not only include the image forming job, but also include any process necessary for performing the image forming job.

[0013] In addition, an “image scanning apparatus” may refer to an apparatus which scans an image of a document to generate a scan image. Examples of such an image scanning apparatus include a printer, a scanner, a copier, a facsimile, or a multi-function peripheral (MFP) serving functions of these in combination as one apparatus, and the like. If the image scanning apparatus is a printer, a scanner, a copier, a facsimile, or an MFP capable of performing an image forming job, the image scanning apparatus may also be referred to as an image forming apparatus.

[0014] In addition, “scan data” may refer to a scan image generated by using the image scanning apparatus, may be a black-and-white image or a color image, and may have various types of file formats (e.g., BMP, JPG, TIFF, PDF, and the like).

[0015] Further, a “main scan direction” may refer to a scan direction in which an image sensor scans a document, and may be, for example, a direction orthogonal to a movement direction of the document. [0016] In addition, a “sub-scan direction” may refer to a movement direction of the document.

[0017] In an image scanning apparatus, a brightness level of a document may increase and a tone of a scan image may be reduced due to a flare generated by diffused reflection of light reflected from a white area of the document to the inside of a sensing device when scanning the document. This may have an effect that a certain amount of white light is applied to the entire document in terms of color, and accordingly, color concentration may be deteriorated which may cause quality degradation of the image scanning apparatus.

[0018] An example image scanning apparatus may compensate a flare phenomenon. In addition, when flare compensation is applied to an image scanning apparatus that uses a multi-optical system for performing scanning by dividing one document into a plurality of areas via a plurality of image sensors, the flare generated for each of the plurality of image sensors may be compensated, respectively. Accordingly, an example image scanning apparatus may generate a scan image having a generally uniform brightness level by reducing a level difference that may be generated on the scan image of each area of a document to be scanned.

[0019] FIG. 1 is a block diagram illustrating an image scanning apparatus according to an example.

[0020] Referring to FIG. 1 , an image scanning apparatus 100 may include a sensing device 110, a memory 120, and a processor 130.

[0021] The sensing device 110 may scan a document. For example, the sensing device 110 may include at least one image sensor and the image sensor may scan image information of the document from light reflected from the document. Such an image sensor may include a charge coupled device (CCD) or a CMOS image sensor (CIS) disposed in a main scan direction. The image sensor may be disposed on a lower end of a flatbed or may be disposed in an automatic document feeder (ADF).

[0022] The memory 120 may store data for image processing. For example, the memory 120 may store a program for performing image processing of a processor 130 which will be described later, a signal scanned by the sensing device 110, data processed by the processor 130, and the like.

[0023] For example, the memory 120 may store a flare factor to be used for compensating an occurrence of flare. Accordingly, the image scanning apparatus 100 may perform a flare compensation process with respect to a signal scanned by the sensing device 110 by using the flare factor stored in the memory 120 to generate a compensated scan image at the time of a scan job. A description regarding an example calculation of a flare factor and a flare compensation using a flare factor will be described later.

[0024] The memory 120 may be a volatile memory, such as a dynamic random access memory (DRAM) or a static random access memory (SRAM), or a non-volatile memory, such as a hard disk drive (HDD), a solid stage drive (SSD), and a flash memory. In an example, the memory 120 may be a combination of the volatile memory and the non-volatile memory.

[0025] The processor 130 may control an element in the image scanning apparatus 100. For example, the processor 130 may be implemented as a central processing unit (CPU), an application specific integrated circuit (ASIC), and the like and may detect whether a scan command is input from a user. Herein, the scan command may be input via an input device (e.g., input device 180, FIG. 2) provided in the image scanning apparatus 100 or may be input via a communication device (e.g., communication device 160, FIG. 2) as a signal from an external apparatus.

[0026] When a scan command for a document is input, the processor 130 may control the sensing device 110 to perform the scan job.

[0027] For example, when a scan command for a test document including a test image is input, the processor 130 may control the sensing device 110 to perform the scan job of scanning the test document.

[0028] In an example, the test document may refer to a document including a test image with a changeable ratio between a black area and a white area in a sub-scan direction. In this case, when the scan job of the test document is performed, a black level in a signal output with respect to each scan line may change according to a change in a ratio between the black area and the white area with respect to each scan line. In an example, if the ratio of the white area is high in the scan line, the effect of a flare may increase which may cause an increase in the black level of the output signal. If the ratio of the black area increases, the black level of the output signal may decrease.

[0029] The processor 130 may calculate a flare factor for flare compensation. In an example, the flare factor for flare compensation is calculated using a plurality of signal values output with respect to each of a plurality of scan lines on the sensing device 110.

[0030] Herein, flare compensation may refer to compensation performed to reduce an output signal level that is increased due to the flare.

[0031] The effect of the flare generated on the sensing device 110 may vary. For example, the effect of the flare may vary depending on a deviation of surface roughness of components included in the sensing device 110. Also, the effect of the flare may vary depending on a product tolerance of the image scanning apparatus 100 due to foreign materials, contamination, and the like that may have been introduced during manufacturing of the image scanning apparatus 100. For example, if a signal obtained by scanning one area of each document using a plurality of image sensors is output, flare factors for the image sensors may vary since the effects of the flare generated on the image sensors may vary.

[0032] The processor 130 may perform a test document scan regarding each of a plurality of image sensors and perform compensation regarding a scan image using the flare factor calculated for each of the image sensors. Accordingly, it is possible to perform the flare compensation at a uniform level by calculating the flare factor corresponding to each of the plurality of image sensors, regardless of the product tolerance.

[0033] In addition, the processor 130 may store the calculated flare factor in the memory 120. If the sensing device 110 includes a plurality of image sensors disposed in the main scan direction, the processor 130 may calculate a flare factor for each of the plurality of image sensors and store each flare factor in the memory 120.

[0034] When a scan command is input after calculating a flare factor, the processor 130 may control the sensing device 110 to perform a scan job by scanning a document provided to the image scanning apparatus 100. The processor 130 may compensate a signal value output from the sensing device 110 using the flare factor stored in the memory 120.

[0035] The processor 130 may generate an image by using the compensated signal value. Therefore, it is possible to provide a scan image with compensated flare phenomenon and improve a quality of the image scanning apparatus.

[0036] FIG. 2 is a block diagram illustrating an image scanning apparatus according to an example.

[0037] Referring to FIG. 2, the image scanning apparatus 100 may include the sensing device 110, the memory 120, the processor 130, an illumination device 140, a driving device 150, a communication device 160, a display 170, and an input device 180.

[0038] The sensing device 110 may include a plurality of image sensors 110-1 , 110-2, ... , and 110-n. In an example, the plurality of image sensors may be consecutively disposed in the main scan direction. The plurality of image sensors 110-1 , 110-2, ... , and 110-n may divide a document and perform the scan job regarding each of the divided areas.

[0039] The illumination device 140 may emit light to a document by using a light emitting diode (LED) light source. Herein, the LED light source may be able to adjust a brightness value. For example, the LED light source may output light with a brightness value corresponding to a magnitude of an input current. The LED light source may also continuously output light or may intermittently output light according to whether a current is input. The LED light source may be a white (W) LED light source or may also be a module type in combination of a red (R) LED, a green (G) LED, and a blue (B) LED.

[0040] In an example, the illumination device 140 may further include a member such as a polarizing plate or the like in order to uniformly emit light to the document.

[0041] The driving device 150 may refer to a device for transferring the document. If the image scanning apparatus 100 is an automatic document feeder type, the driving device 150 may include a device structure and a motor for moving the document on a document movement path.

[0042] In an example, if the image scanning apparatus 100 includes both a flatbed and an automatic document feeder, the driving device 150 may include separate driving sources for driving a device for transferring the document and for driving a device for moving the sensing device 110.

[0043] The communication device 160 may be connected to a terminal device (not illustrated) such as a mobile device (e.g., a smartphone, a tablet personal computer (PC), etc.), a PC, a laptop PC, a personal digital assistant (PDA), a digital camera, and the like to transfer a scan image or scan data prestored in the memory 120 to the terminal device. For example, the communication device 160 may be formed to connect the image scanning apparatus 100 to an external apparatus and may be connected via a universal serial bus (USB) port or a wireless communication (e.g., Wi-Fi 802.11 a/b/g/n, near field communication (NFC), or Bluetooth) port, in addition to connection to the terminal device via a local area network (LAN) or the Internet.

[0044] In addition, if the image scanning apparatus 100 is an MFP capable of performing a printing job and a copying job, a scan command may be a copying command by using a scan function. In an example, the image scanning apparatus 100 may receive a scan command via the input device 180, but there is no limitation thereto, and the scan command may be received from a terminal device (not illustrated) via the communication device 160.

[0045] The display 170 may display various pieces of information provided from the image scanning apparatus 100. For example, the display 170 may display a user interface window for selecting various functions or options provided by the image scanning apparatus 100. Such display 170 may be a monitor such as a liquid crystal display (LCD), a cathode ray tube (CRT), an LED, an organic LED (OLED), and the like, and may also be implemented as a touch screen for simultaneously performing a function of the input device 180, which will be described later.

[0046] The display 170 may display a control menu for performing a function of the image scanning apparatus 100. Using the display 170, a user may input a scan command on the displayed user interface window. Herein, the scan command may refer to a command for performing the scan job or may be scan- to-server, scan-to-Digital Living Network Alliance (DLNA), a scan-to-cloud command, and the like for transmitting the scanned job to a server.

[0047] The input device 180 may receive a selection of a function and a control command regarding the corresponding function from the user. The function herein may include a scan function, a copy function, a fax transmission function, and the like. The input device 180 may be implemented as a plurality of buttons, a keyboard, a mouse, and the like and may also be implemented as a touch screen for performing the functions of the display 170 at the same time.

[0048] FIG. 3 is a diagram illustrating a shape of an image scanning apparatus according to an example.

[0049] Referring to FIG. 3, an image scanning apparatus 200 may include a first scan device 201 of a flatbed type for scanning a document placed on a flat plate (i.e., a platen) and a second scan device 202 of an automatic document feeder for consecutively scanning documents on an automatic feeder.

[0050] The first scan device 201 may be a scan device of a flatbed type. A document may be placed on the flat plate and a sensing device, having an image sensor and located a lower portion of the flat plate on which the document is placed, may move to scan the document.

[0051] The second scan device 202 may be a scan device of an automatic document feeder type. A plurality of documents may be placed on a feeder, the documents may move to a paper movement path in sequence, and an image sensor positioned on the paper movement path may scan the documents. The second scan device 202 may be a one-sided scan device for scanning one side of the documents or may be a double-sided scan device for scanning both sides of the documents.

[0052] Hereinabove, it is described that the first scan device 201 and the second scan device 202 have individual sensing devices, respectively. However, this is an example and in other implementations, one sensing device may be commonly used in the first scan device 201 and the second scan device 202.

[0053] Hereinafter, an example flare factor calculation operation will be described with reference to FIGS. 4 and 5.

[0054] FIG. 4 is a diagram illustrating an example of an image included in a test document.

[0055] Referring to FIG. 4, a test document may be a document provided to the image scanning apparatus 100 for calculating a flare factor and may include a specific image. For example, the test document may include a test image having a changing ratio between a black area and a white area in a sub-scan direction S. Accordingly, the ratio between the black area and the white area included in each scan line may change and a black level of a signal output from the sensing device 110 with respect to each scan line may change. In an example, if the ratio of the white area to the black area is high in the scan line, the effect of the flare may increase which may cause an increase in the black level of the output signal. On the other hand, if the ratio of the black area to the white area increases, the black level of the output signal may decrease.

[0056] The image included in the test document is not limited to the example illustrated in FIG. 4. That is, the image included in the test document may be any of various images with a changeable black and white ratio, in addition to the type in which the ratio of the black area and the white area changes linearly along the sub-scan direction S, as illustrated in FIG. 4. In addition, the image may not be the image including a black area and a white area, but may be an image with a changeable ratio between a relatively dark area and a bright area along the sub-scan direction S.

[0057] The processor 130 may obtain a black level y of a signal output from the sensing device 110 for each scan line and a value of a mean level x. Herein, the mean level x may be a mean brightness level of the corresponding scan line. [0058] The processor 130 may calculate a changed value of the black level y according to a change in mean level x of the signal output from the sensing device 110 as a flare factor.

[0059] FIG. 5 is a diagram illustrating an operation of calculating a flare factor according to an example.

[0060] FIG. 5 illustrates a graph of black level y with respect to a mean level x that is obtained regarding a plurality of signals output from the sensing device 110 which has performed the scan job regarding the test document.

[0061] The processor 130 may store the flare factor calculated as described above in the memory 120 and compensate the signal output from the sensing device 110 by using the flare factor when scanning the document.

[0062] As an example, the processor 130 may apply the flare factor to the value of the mean level x of the signal output from the sensing device 110 regarding the document to calculate a flare compensation value.

[0063] The effect of the flare may vary depending on the ratio between the black area (dark area) and the white area (bright area) included in the scan line, and accordingly, the flare compensation value may vary depending on the mean level of the scanned signal. In other words, when scanning the document, if the mean level of the scan line is high, the flare compensation value may increase.

[0064] The processor 130 may compensate the signal value output from the sensing device 110 regarding the document to decrease by the flare compensation value by using the calculated compensation value and generate an image by using the compensated signal value. Therefore, it is possible to provide improved image quality by generating a scan image with compensated flare phenomenon.

[0065] The processor 130 may calculate a signal value output by the sensing device 110 while the illumination device 140 is turned off as a reference compensation value and may compensate the signal by subtracting the reference compensation value and the flare compensation value from the signal value output from the sensing device 110. Therefore, it is also possible to compensate the black level that is generally generated.

[0066] FIG. 6 is a diagram illustrating an image scanning apparatus including a plurality of image sensors according to an example and FIG. 7 is a diagram illustrating an operation of calculating a flare factor for each of a plurality of image sensors.

[0067] Referring to FIG. 6, the sensing device 110 may include the plurality of image sensors 110-1 , 110-2, ... , and 110-n which are consecutively disposed in the main scan direction M. The plurality of image sensors may divide one document into areas consecutively disposed in the main scan direction M, that is, areas corresponding to the plurality of image sensors, respectively, to perform the scan job regarding each of the divided areas.

[0068] FIG. 7 illustrates an enlarged part of one scan line in the image scanning apparatus 100 including the plurality of image sensors consecutively disposed in the main scan direction M. The scan line may be divided into a plurality of areas in the main scan direction M and the areas may be subjected to the scan job by image sensors different from each other, respectively.

[0069] Referring to FIG. 7, images scanned in an (i-2)-th area and an (i-1 )- th area include only the black area, and accordingly, the effect of the flare phenomenon is not significant. However, an i-th area includes the black area and the white area. In that case, the black level of the black area may increase due to light reflected by the white area, and it is necessary to compensate for this occurrence.

[0070] In this case, the mean level obtained from the signal output by the image sensor from each area, and the flare factor value corresponding to each of the image sensors may vary. The processor 130 may perform the flare compensation regarding each area by considering the mean level obtained regarding each area and the flare factor of the image sensor which has scanned each area. Accordingly, it is possible to perform the flare compensation according to the mean level of each divided area regardless of the product tolerance of each image sensor.

[0071] Further, it is possible to decrease a level difference that may be generated on the scan image of each area of the document to be scanned, thereby generating a scan image with a uniform brightness level.

[0072] FIG. 8 is a flowchart illustrating a method for controlling an image scanning apparatus according to an example.

[0073] Referring to FIG. 8, when a scan command regarding a document with a changeable ratio between a black area and a white area in the sub-scan direction is input, the image scanning apparatus 100 may calculate a flare factor for flare compensation by using a plurality of signal values output from the sensing device regarding the document in operation S810.

[0074] For example, the image scanning apparatus 100 may calculate a changed black level value according to a mean level change of the signal output from the sensing device regarding the document as the flare factor.

[0075] In addition, the image scanning apparatus 100 may store the calculated flare factor in the memory in operation S820.

[0076] When the scan command is input after calculating the flare factor, the image scanning apparatus 100 may compensate the signal value output from the sensing device by using the stored flare factor in operation S830.

[0077] When the signal output from the sensing device is received according to input of the scan command, the image scanning apparatus 100 may obtain a mean level value of each output signal regarding each scan line and may calculate a flare compensation value regarding each scan line by multiplying the stored flare factor by the mean level value corresponding to each scan line. The image scanning apparatus 100 may calculate a final compensation value by adding the compensation value calculated using the flare factor to a reference compensation value. In various examples, the reference compensation value may be a signal value output by the sensing device or an optical black value provided by the image sensor when the illuminance device is turned off. In addition, the image scanning apparatus 100 may perform the compensation so that the output signal regarding each scan line decreases by the final compensation value corresponding to each scan line.

[0078] The image scanning apparatus 100 may generate an image by using the compensated signal value in operation S840. The image scanning apparatus 100 may transmit the generated scan image to another apparatus or may perform the print job regarding the scan image.

[0079] Therefore, the image scanning apparatus 100 may generate the scan image with the compensated flare phenomenon to improve a quality of the scan image.

[0080] A non-transitory computer-readable medium storing a program for the flare compensation according to an example of the disclosure may be provided.

[0081] The non-transitory computer-readable medium is not a medium storing data for a short period of time such as a register, a cache, or a memory, but may refer to a medium that semi-permanently stores data and is readable by a machine. For example, the various applications or programs described above may be stored and provided to the non-transitory computer-readable medium such as a CD, a DVD, a hard disk drive, a Blu-ray disc, a USB, a memory card, and a ROM.

[0082] While examples of the disclosure have been shown and described, the disclosure is not limited to the aforementioned examples, and it is apparent that various modifications can be made by those having ordinary skill in the technical field to which the disclosure belongs, without departing from the gist of the disclosure as claimed by the appended claims. Also, it is intended that such modifications are not to be interpreted independently from the technical idea or prospect of the disclosure.

Claims

WHAT IS CLAIMED IS:

1 . An image scanning apparatus comprising: a sensing device to scan a document; a memory; and a processor to: based on a scan command to scan a document having a changeable ratio between a black area and a white area in a sub-scan direction being input, calculate a flare factor for flare compensation by using a plurality of signal values output from the sensing device regarding the document, store the flare factor in the memory, based on a scan command being input after calculating the flare factor, compensate a signal value output from the sensing device by using the stored flare factor, and generate an image by using the compensated signal value.

2. The image scanning apparatus according to claim 1 , wherein the sensing device comprises a plurality of image sensors consecutively disposed in a main scan direction, and wherein the processor is to calculate the flare factor for each of the plurality of image sensors.

3. The image scanning apparatus according to claim 1 , wherein the processor is to calculate a changed black level value according to a change in a mean level of a signal output from the sensing device regarding the document as the flare factor.

4. The image scanning apparatus according to claim 1 , wherein the processor is to calculate a flare compensation value by applying the flare factor to a mean level value of the signal output from the sensing device regarding the document.

5. The image scanning apparatus according to claim 4, further comprising: an illumination device to emit light, wherein the processor is to calculate a signal value output by the sensing device, while the illumination device is turned off, as a reference compensation value.

6. The image scanning apparatus according to claim 5, wherein the processor, based on the scan command being input after calculating the flare factor, is to generate an image by using a signal value compensated by subtracting the flare compensation value and the reference compensation value from the signal value output from the sensing device.

7. The image scanning apparatus according to claim 1 , wherein the ratio between the black area and the white area included in the document changes linearly along the sub-scan direction.

8. A method for controlling an image scanning apparatus, the method comprising: based on a scan command to scan a document having a changeable ratio between a black area and a white area in a sub-scan direction being input, calculating a flare factor for flare compensation by using a plurality of signal values output from a sensing device regarding the document; storing the calculated flare factor in a memory; based on a scan command being input after calculating the flare factor, compensating a signal value output from the sensing device by using the stored flare factor; and generating an image by using the compensated signal value.

9. The method according to claim 8, wherein the sensing device comprises a plurality of image sensors 16 consecutively disposed in a main scan direction, and wherein the calculating of the flare factor comprises calculating the flare factor for each of the plurality of image sensors.

10. The method according to claim 8, wherein the calculating of the flare factor comprises calculating a changed black level value according to a change in a mean level of a signal output from the sensing device regarding the document as the flare factor.

11. The method according to claim 8, wherein the compensating comprises calculating a flare compensation value by applying the flare factor to a mean level value of the signal output from the sensing device regarding the document.

12. The method according to claim 11 , wherein the compensating comprises calculating a signal value output by the sensing device, while an illumination device which emits light to a document is turned off, as a reference compensation value.

13. The method according to claim 12, wherein the compensating comprises, based on the scan command being input after calculating the flare factor, compensating the signal value output from the sensing device by subtracting the flare compensation value and the reference compensation value from the signal value output from the sensing device, and wherein the generating of the image comprises generating the image by using the compensated signal value.

14. The method according to claim 8, wherein the ratio between the black area and the white area included in the document changes linearly along the sub-scan direction.

15. A non-transitory computer-readable recording medium storing a 17 program for flare compensation of an image scanning apparatus, the non- transitory computer-readable recording medium comprising: instructions to, based on a scan command to scan a document having a changeable ratio between a black area and a white area in a sub-scan direction being input, calculate a flare factor for flare compensation by using a plurality of signal values output from a sensing device regarding the document; instructions to store the calculated flare factor in a memory; instructions to, based on a scan command being input after calculating the flare factor, compensate a signal value output from the sensing device by using the stored flare factor; and instructions to generate an image by using the compensated signal value.